Aircraft are commonly equipped with Cabin Pressure Control Systems (CPCSs), which maintain cabin air pressure within a desired range to increase passenger comfort during flight. A typical CPCS may include a controller, an actuator, and an outflow valve. The outflow valve is typically mounted either on a bulkhead of the aircraft or on the outer skin surface of the aircraft, and selectively fluidly couples the aircraft cabin and the atmosphere outside of the aircraft. During operation, the controller commands the actuator to move the outflow valve to various positions to control the rate at which pressurized air is transferred between the aircraft cabin and the outside atmosphere, to thereby control the pressure and/or rate of change of pressure within the aircraft cabin. The controller may be configured to command the actuator to modulate the outflow valve in accordance with a predetermined schedule or as a function of one or more operational criteria. For example, the CPCS may additionally include one or more cabin pressure sensors to sense cabin pressure and supply pressure signals representative thereof to the controller. By actively modulating the outflow valve, the controller may maintain aircraft cabin pressure and/or aircraft cabin pressure rate of change within a desired range.
In some aircraft, the outflow valve may be positioned on the aircraft outer skin surface such that, when pressurized air is exhausted from the cabin, the exhausted air may provide additional forward thrust to the aircraft. Thus, outflow valves may sometimes be referred to as thrust recovery valves. Many thrust recovery valves often include two valve doors with multiple actuation linkages to enable proper sealing, reduce drag, and optimize valve door positioning for cruise thrust creation. In order to maximize the thrust produced by two-door thrust recovery valves, the valve doors are shaped and sealed so that air flow is directed between the doors during flight.
In addition to the above, it is noted that most commercial aircraft are required to be designed to withstand highly unlikely, yet postulated events. One of these events is a loss of pressurized air flow into the aircraft cabin during flight. In particular, the ventilation systems in such aircraft are designed, in the unlikely occurrence of a loss of the pressurized air flow, to provide at least 0.4 lb/min of fresh air for each occupant to prevent CO2 poisoning. Therefore, in addition to an outflow valve or thrust recovery outflow valve, most commercial aircraft include one or more emergency ram air inlet valves, actuators, and control electronics. In the unlikely occurrence of a loss of pressurized air flow, these ram air inlet valves may be opened to implement what is referred to herein as a “ram air recovery function,” in which ambient air is forced into the aircraft cabin.
The ram air inlet valves, actuators, and control electronics are typically not used, but are provided only for the unlikely occurrence of a loss of pressurized air flow to the cabin. Thus, these components unnecessarily increase aircraft weight and cost for a vast majority of flight conditions. Accordingly, it would desirable to incorporate the functionality of the ram air inlet valves into another, existing aircraft system, such as the CPCS, and more specifically into CPCS thrust recovery outflow valves.